Production of colored film-forming materials



colored textiles, fi-lmsgand the like.

Patented Mar. I4, 1944 PRODUCTION or COLORED FILM-FORMING MATERIALS Robert Pierce Roberts, Spondon, near Derby, England, assignor to Celanese Corporation ica. a corporation of Delaware of Amer- No Drawing. Application February 12, 1941, Serial No. 378,636. In Great Britain March'13, 19.40

G-CIaims 7 (Cl. loo- 92),

This invention relates to improvements in the production of colored film-forming materials and It is more to 'be used for the manufacture of colored filaments, films and the like.

particularly concerned with the coloration of film-forming materials which are-soluble in organic solvents by means of vat dyestuffs.

' A major consideration in the dyeing of textile materials isfastness of-the colorations to scouring and in addition f-astness to light and other I agencies. The vat dyestuifs, e. g. of the indigoid.

In order that the dyestuii' particles should be as fine as possible in the final complexof filmforming'material and vat dyestuil the suspension of the leuco compound is preferably formed by acidification of an alkaline vat. The acid used for the acidification is preferably itself a solvent thio-indigoid and anthraquinone series, offer in the field of the natural textiles very considerable advantages in relation to fastness generally. However, for the major part they have little appli-cation to textiles of cellulose acetate and similar filmcformingtmaterials, since they havelittle or no aflinity for these materials. Proposals have been made to incorporate vat dyestufis in cel lulose' acetate spinning solutions so as to'obtain colored filaments, but the proposals have up to the present not been applied commercially on any substantial scale, principally because of the difliculty of obtaining a good compounding of the vat dyestuff with the cellulose acetate so as to obtain a complex which is fast to rubbing: and scouring.

According to the present invention, a complex of cellulose acetate or other suitable film-forming material soluble in organic solvents and a vat dyestufi eminently suitable for the production of for the film forming'substance, as for example acetic] acid or other [organic acid, and may be addcd'to' thev alkaline vat'in such an excess that the addition of the suspension of the leuco com pound in the aqueous acid to the solution of the film-'formingmaterial produces no precipitation of that material even locally. Again, instead of using uiiicient acetic or other organic acid both to liberate the free leuco compound and to prevent precipitation of the' film-iorming material,

an amount'of acid may be used which is less though sufiici'ent to liberate the free leuco compound, the balance being replaced by suflicient of another water-miscible organic liquid e. g., acetone, to prevent precipitation of the film-- forming material when the suspension of the free leuco compound is mixed with the solution of film-forming materlal.

Most advantageously the alkaline vat is acidified with acetic acid used in excess, and the susfilaments and also for the production of films,

sheets and the like, is formed by intimately mix-i ing an aqueous suspension of the free leuco compound of the vat'dyestufl with asolution of the cellulose'acetate or other film-forming material pension of the leuco compound in the aqueous acetic acid is added to an acetic acid solution of the cellulose acetate or other film-forming material.

When aithorough admixture of the solutionof the'film-forming; material with the in an organic solvent in such proportions that,

after the mixing, the cellulose acetate or the like is an in solution. After such intimate admixi ture. precipitation of the cellulose acetate results in the production of a complex in which the dye stuff is so intimately held that filaments, films and other products formed therefrom by shaping and setting solutions thereof or solutions of fiimforming materials colored therewith are extremely fast to scouring. Further, products can be obtained in which the dyestufis are in such finely divided form that solutions of the products can. without substantial loss of color, pass through the filters usually associated with spinning nozzles used for the spinning of artificial filaments; Moreover products can be prepared which contain high proportions of vat dye, e. g. 5 to 25 per cent or more bas'edon the weight of filmformlng material. These products are suitable for mixing with uncolored film-forming material 'suspension' of the leuco compound has been obtained, the film-forming material is precipitated,

and during the precipitation it the leuco compound. The complex may then be filtered oil, washed and dried in the usual way. v During this process oxidation of the leuco compound takes place, and at the end of the drying process it is usually complete. Even, however, if it is not complete at thisstage, when the {complex is subsequently dissolved in a volatile organic solvent and. spun into filaments in the usual way, the oxidation proceeds during the spinning process itself. In very exceptional cases it may be desirable to apply a special oxidising treatment, e. g'., with hycarries with it drogen peroxide, to the filaments after spinning.

However, none of the leuco compounds yet tried is so resistant as to require such after treatment.

If desired the solution of the film-forming material which has been thoroughly admixed with the suspension of the leuco vat dyestufl may be spun directly, but this is less advantageous vention, it is preferable, beforeforming the vat and precipitating the leuco compound, to free the dyes from the diluents with which the commercial products are usually associated. For this purpose, digestion with a dilute solution of hydrochloric acid for several hours at an elevated temperature is usually sufllcient. I

The following example illustrates the invention, the parts given being by weight. 7

35 parts of purified Caledon Brilliant Blu 36 (purified by digestion for several hours with 2% hydrochloric acid at 80 C.) are made into a uniform suspension in 2500 parts of water. 110 parts of caustic soda are then added, and the whole heated to 60 C. '70 parts of hydro-sulphite are added gradually while stirring. When solution of the reduced dyestuif is complete, 2500 parts of glacial acetic acid are added, followed by 3000 parts of a solution of cellulose acetate in acetic acid, the whole being vigorously stirred throughout the addition. No precipitation of cellulose acetate takes place, and a fine suspension of the leuco dyestuff in the viscous solution of cellulose acetate is produced. The whole is poured into excess water so as to precipitate the cellulose acetate and the whole of the dyestuff. The complex is filtered off, washed thoroughly until free from acetic acid, and dried in the usual way. The amount of color'removed from the complex during the washing operation is negligible. The complex contains considerably more dyestufl' than is necessary for the production of articles with a full shade of blue, for which purpose about 0.5% of dyestuif on the weight of the cellulose acetate is sufficient. The complex is therefore used as a color master material for admixture with uncolored cellulose acetate for spinning purposes. Thus the amount of complex obtained above is suitable for the coloration of about 7000 parts of cellulose acetate dissolved in the appropriate quantity of acetone for spinning. The colored dope thus prepared is filtered in the usual way and spun into filaments which have a deep blue color.

As already indicated, the invention is applicable quite broadly to the production of materials colored with any vat dyestufls, for example those of the indigoid, thio-indigoid, anthraquinone and dibenzpyrenequinone series. Examples of dyestuffs in addition to those mentioned above are Caledon Jade Green, Indanthrene Golden Yellow RK, Durindone Red BS, Indanthrene Bril-. liant VioletBBK, Caledon Red BN and 'Indanthrene Grey 63.

Reference has been made to cellulose acetate as the film-forming material. The invention is applicable to the coloration of other film-form- Having described my invention, what I desire to secure by Letters Patent is:

1. Process for the production of a colored cellulose compound which is insoluble in water, soluble in a water miscible organic liquid, and selected from the group consisting of cellulose esters and ethers, which comprises mixing an aqueous suspension of a free leuco compound of vat dye with a solution of such cellulose compound in a a suspension of a free leuco compound of a vat water miscible organic liquid in such proportions that after the mixing the cellulose compound is still in solution, and then precipitating the cellulose compound from the solution.

2. Process for the production of a colored cellulose acetate product, which comprises mixing a solution of cellulose acetate in acetic acid with dye, said suspension being made by acidifying an aqueous alkaline solution of a leuco compound of a vat dye with so much acetic acid that no precipitation of cellulose acetate occurs during the mixing, and thereafter precipitating the cellulose acetate by the action of water.

3. Process for the production of a colored cellulose compound which is insoluble in water,

soluble in a water miscible organic liquid, and

selected from the group consisting of cellulose esters and ethers, which comprises mixing an aqueous suspension of a free leuco compound of a vat dye with a solution of such cellulose compound material in a water-miscible organic liquid in such proportions that; after the mixing, the

cellulose compound material is still in solution,-

andthen precipitating the cellulose compound material from the solution by the action of water.

4. Process for the production of a colored cellulose compound which is insoluble in water, soluble in a water miscible organic liquid, and selected from the group consisting of cellulose esters and ethers, which comprises mixing a solution of such cellulose'compound in a water-miscible organic liquid with an aqueous suspension of a free leuco compound of a vat dye containing-so much water-miscible solvent for the cellulose compound that no precipitation occurs during the mixing, and thereafter precipitating the cellulose compound from its solution.

5. Process for the production of a colored cellulose aceate product, which comprises mixing an aqueous suspension of a free leuco compound of a vat dye with a solution of cellulose acetate in a water-miscible organic liquid in such proportions that, after the mixing, the cellulose acetate is still in solution, and then precipitating the "cellulose acetate from the solution.

, 6. Process for the production of a colored cellulose acetate product, which comprises mixing a ing materials and of articles made therefrom, for

' solution of cellulose acetate in a water-miscible organic liquid with an aqueous suspension of a free leuco compound of a vat dye containing so much water-miscible solvent for the cellulose acetate that no precipitation occurs during the mixing, andthereafter precipitating the cellulose acetate from its solution.

' ROBERT PIERCE ROBERTS. 

